Method and system for preserving data of a storage device

ABSTRACT

A method and system for preserving data of a storage device are disclosed. In one embodiment, the method includes determining a number of times data is written to a first track in a first region of a storage medium, and rewriting data from a second track that is adjacent to the first track in the first region if the number of times data is written to the first track in the first region exceeds a first predetermined threshold. The method further includes determining a number of times data is rewritten to the second track in the first region, and relocating data from the second track in the first region to a second region of the storage medium if the number of times data is rewritten to the second track in the first region exceeds a second predetermined threshold.

SUMMARY

In one aspect, the present disclosure provides a method that includesdetermining a number of times data is written to a first track in afirst region of a storage medium, and rewriting data from a second trackthat is adjacent to the first track in the first region if the number oftimes data is written to the first track in the first region exceeds afirst predetermined threshold. The method further includes determining anumber of times data is rewritten to the second track in the firstregion, and relocating data from the second track in the first region toa second region of the storage medium if the number of times data isrewritten to the second track in the first region exceeds a secondpredetermined threshold.

In another aspect, the present disclosure provides a system thatincludes a storage medium including a first region with a target trackand an adjacent track to the target track, and a controller. Thecontroller is configured to rewrite data from the adjacent track if anumber of times data is written to the target track exceeds a firstthreshold amount. The controller is further configured to relocate datafrom the adjacent track in the first region to a second region of thestorage medium if a number of times data is rewritten to the secondtrack exceeds a second threshold amount.

In another aspect, the present disclosure provides a method thatincludes receiving a write command, and searching a lookup table where anumber of writes to a logical block address (LBA) of a first track in afirst region of a storage medium is recorded when receiving the writecommand. The method further includes rewriting data from a second trackthat is adjacent to the first track in the first region if the number ofwrites of the LBA of the first track of the first region exceeds a firstpredetermined threshold of writes, and searching a lookup table where anumber of rewrites to an LBA of the second track in the first region isrecorded when receiving the write command. The method further includesrelocating data from the second track in the first region to a secondregion of the storage medium if the number of writes of the LBA of thesecond track in the first region exceeds a second predeterminedthreshold of writes, and rearranging the LBA of the second track of thefirst region by interchanging the LBA of the second track of the firstregion with an LBA of the second region.

These and other aspects of the present disclosure will be apparent fromthe detailed description below. In no event, however, should the abovesummaries be construed as limitations on the claimed subject matter,which subject matter is defined solely by the attached claims, as may beamended during prosecution.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the specification, reference is made to the appendeddrawings, where like reference numerals designate like elements, andwherein:

FIG. 1 is a schematic block diagram of one embodiment of a data storagesystem.

FIG. 2 is a schematic cross-section view of one embodiment of a writeelement portion of the head and the magnetic medium of the system ofFIG. 1.

FIG. 3 is a schematic cross-section view of one embodiment of a readelement portion of the head and the magnetic medium of the system ofFIG. 1.

FIG. 4 is a schematic view of signal states for various tracks of amagnetic medium.

FIG. 5 is a flow diagram of one embodiment of a method of preservingdata.

DETAILED DESCRIPTION

In general, the present disclosure relates to various embodiments of amethod and system for preserving data of a data storage device, which,in some embodiments, can minimize data loss due to adjacent track erase(ATE) phenomenon.

The capacity of data storage devices continues to increase. For example,some embodiments of data storage systems utilize magnetic fields toselectively change the magnetic state of magnetic storage media. Onetechnique for increasing the capacity of these types of data storagesystems is to increase the number of tracks per inch (TPI) on themagnetic storage media, which represents the track density of a system.

In some embodiments, a writing element portion of a magnetic head isused to produce a magnetic field that can write data to the magneticmedia. As is further described herein, the magnetic field from thewriting element portion can be incident upon not only a target track butalso tracks that are adjacent to the target track. As the TPI or densityof the magnetic media increases, the likelihood that adjacent tracks areaffected by the magnetic fields from the writing element portion alsoincreases. This overlap of the magnetic field onto adjacent tracks canweaken or even erase the data signal from these tracks, i.e., adjacenttrack erase (ATE) can occur. In other words, the ATE phenomenon canoccur if data is repetitively written in one position (i.e., to a targettrack) because the magnetic field used to write data to the target trackcan affect tracks adjacent to the target track, thereby potentiallydamaging or erasing the data written to the adjacent tracks.

One or more embodiments of the present disclosure can reduce oreliminate the ATE phenomenon by monitoring the number of times data iswritten to a target or first track, and then rewriting data from one ormore tracks that are adjacent to the first track if the number of timesdata is written to the first track exceeds a first predeterminedthreshold. Further, in some embodiments, the number of times data isrewritten to these adjacent tracks can be monitored, and this data canbe relocated to a different region or location of the magnetic storagemedium if the number of times data is rewritten to adjacent tracksexceeds a second predetermined threshold.

The various embodiments of a method and system of the present disclosurecan be used with any suitable data storage systems. For example, FIG. 1is a schematic plan view of one embodiment of a data storage system 10.The system 10 includes data storage medium 18. Medium 18 can be dividedinto data tracks, such as track 30, and a head 28 is positioned adjacentthe data tracks to read data from and store data to a respective track.

The tracks 30 can be provided with head position control informationwritten to embedded servo sectors. Between the embedded servo sectorsare data sectors used for storing data in the form of bit patterns. Thehead 28 can include a read element portion and a write element portion.The write element portion writes input data to the track 30 during writeoperations of the device 10, and the read element portion reads outputdata from the tracks. This output data can be previously stored datathat is being recalled for use in processing, or the data can be servodata used to control the positioning of the head 28 relative to adesired track 30. In some embodiments, medium 18 can be dedicated toproviding servo information for one or more other heads 28.

The system 10 can include any suitable control circuitry. For example,system 10 includes a driving circuit that includes a controller 50 thatcontrols a pre-amplifier (Pre-AMP) 52, a read/write channel (R/Wchannel) 54, a host interface 56, a buffer 62, etc.

The pre-amplifier 52 amplifies a data signal read from the medium 18 bythe magnetic head 28, or amplifies a writing electric current convertedby the read/write channel 54 to be written on the medium through themagnetic head.

The read/write channel 54 converts the signal amplified by thepre-amplifier 52 into a digital signal to be transmitted to a hostdevice (not shown) through the host interface 56, or converts data inputby a user and received through the host interface into a binary datastream to be input to the pre-amplifier.

The host interface 56 transmits a digital signal converted based on datato the host device, or receives user input data from the host device andtransmits it to the read/write channel 54 via the controller 50. Here,the host device refers to elements such as a central processing unit(CPU), an input/output (I/O) controller 50, or the like of a computerthat generally controls and operates the whole computer system involvingthe system 10.

The buffer 62 temporarily stores data transmitted between the hostinterface 56 and the controller 50. Generally, the buffer 62 can includeany suitable memory storage, e.g., dynamic random access memory (DRAM)or nonvolatile memory, like flash memory.

The controller 50 receives data input by a user through the host devicethrough the host interface 56 and outputs it to the read/write channel54 in a data writing mode, and receives a digital signal converted basedon a read signal by the read/write channel and outputs it to the hostinterface 58 in a data reading mode. In some embodiments, controller 50preserves data by rewriting and/or relocating the data that is writtenin a zone or region where the ATE phenomenon is likely to occur as isfurther described herein.

The controller 50 can include any suitable devices or circuitry, e.g.,microcontrollers, etc. In some embodiments, the controller 50 can be inthe form of software or firmware.

As mentioned herein, the ATE phenomenon can occur when a writingoperation is repeatedly performed on a target track. Because themagnetic write field can overlap tracks adjacent to the target trackduring these write operations, the data in these adjacent tracks can beunintentionally weakened or erased. For example, FIG. 2 is a schematiccross-section view of one embodiment of a write element portion 70 ofthe head 28 in a data storing relationship with the medium 18 of thesystem 10 illustrated in FIG. 1. And FIG. 3 is a schematic cross-sectionview of a read element portion 82 of the head 28 in a data readingrelationship with the magnetic medium 18. The head 28 is positionedrelative to a centerline 73 of track 72. The write element portion 70 isselectively energized to produce a magnetic flux field 74 that storesinput data, such as by imparting magnetic transitions in the medium 18.Typically, the fringe effects of the flux field 74 are wider than thewidth of the track 72 as illustrated by a flux density profile 76illustrated in FIG. 3. It has been observed that under certainconditions an advantageously robust flux field 74 can be imparted to aparticular location of track 72 with negligible effects of tail portions77 of the flux density profile 76 that are imparted to adjacent tracks78 and 80. In some embodiments, the fringe effects have been negligiblein part because of the flux strength with which data in the adjacenttracks 78, 80 are stored, in part because of the relatively minimalextent to which the tail portions 77 encroach upon the adjacent tracks,and in part because a read element portion 82 of the head 28 istypically narrower than the write element portion 70. Because of thelatter, with sufficient tracking precision of the head 28 the readelement portion 82 is capable of reading a centrally disposed portion ofthe entirety of the stored data.

However, as track density increases, the width of track 72 decreases,thereby potentially making it more challenging for the read elementportion 82 to only read track 72. Further, repeated writes to the sameportion of the medium 18, such as to a particular sector, or to aparticular track or a band of tracks, can affect the integrity of thedata that is stored in adjacent tracks 78, 80. As used herein, the term“writes” refers to the writing of data to a particular track or regionof a magnetic storage medium. Further, these kinds of repeated writingsare typical of activities commonly associated with the continualupdating of stored information. These adverse effects can be exacerbatedby off-track budgeting that permits the storing and retrieving of datawith the head 28 being disposed in a somewhat nonaligned relationshipwith the centerline 73 of track 72.

The ability of the storage medium to reliably “hold” a stored directionof magnetization is related to a material property of the grains ofmagnetic material known as anisotropy energy. As areal density hasincreased, the grain size has correspondingly decreased to maintain therequisite number of grains for adequate thermal stability. However, theanisotropy energy of each grain is proportional to its size, so therelatively smaller grains are more susceptible to thermal decay(superparamagnetic effect). It has been observed that the flux fringeeffects from a large number of repeated writes to a particular trackproduces adverse cumulative effects on the adjacent tracks.

FIG. 4 is a schematic view of signal states of a first or target track90 and adjacent tracks 92, 94 (e.g., second and third tracks). Alsoshown are additional target tracks 96, 98. The first track 90 has beenwritten to more than 10,000 times. As shown in FIG. 4, the data signalsfrom the adjacent tracks 92, 94 are weakened by side fields of thewriting element portion as the magnetic head writes to first track 90.That is, when a multi-writing operation is performed on the first track90 more than a certain number of times (e.g., more than 10,000 times asshown in FIG. 4), the signal states of the adjacent tracks 92, 94 canexperience signal degradation.

The present disclosure provides various embodiments of a method andsystem that can address this signal degradation of tracks that areadjacent to target tracks, thereby reducing the ATE phenomenon. Forexample, FIG. 5 is a flow diagram of one embodiment of a method 100 forpreserving data. The method 100 is described in reference to the storagesystem 10 of FIG. 1. The method can be implemented using any suitabledevices or circuitry, e.g., controller 50 of FIG. 1.

A write command is given to commence a write operation at 102. A numberof times data is written to a first track in a first region of a storagemedium (e.g., storage medium 18) is determined at 104 using any suitabletechnique. For example, in some embodiments, controller 50 can search alookup table where the number of writes to a logical block address (LBA)of the first track in the first region is recorded when receiving thewrite command.

Here, the LBA means a series of sector and/or track numbers allocated tothe respective sectors and tracks of the magnetic medium, e.g., medium18 of FIG. 1 (e.g., sequentially allocated by giving “0” to the firstsector) in logical block addressing as one technique for assigning thesector address of the disk, in which one LBA assigns one sector on thedisk.

In some embodiments, when a writing command is input to controller 50and a writing operation starts, the lookup table where the number ofwrites performed to a specific LBA is recorded and can be searched at104.

The lookup table can be stored, e.g., in a maintenance cylinder of themagnetic medium 18 and uploaded to a buffer (e.g., buffer 62 of FIG. 1)when the device 10 is powered on. That is, in some embodiments, thelookup table can be uploaded from the media 18 to the buffer and thensearched.

In some embodiments, if the lookup table has no LBA for assigning thefirst track in the first region for the writing in response to thewriting command as a result of searching the lookup table, an LBA forassigning the first track can be added to the lookup table. At thistime, the number of writes for the newly added LBA is initialized with“1.” Alternatively, in some embodiments, all LBAs may be previouslystored in the lookup table.

At 106, if the number of times data has been written to the first trackin the first region exceeds a first predetermined threshold (i.e., afirst threshold amount), then data from a second track adjacent to thefirst track in the first region (i.e., an adjacent track) is rewrittenat 108. This first predetermined threshold can be any suitable number ofwrites. In some embodiments, the first threshold can be at least 10times, at least 100 times, at least 1000 times, at least 10,000 times.In other embodiments, the first threshold can be no more than 100,000times. In some embodiments, the threshold can be determined byestimating the number of writes to the first track that may cause datain adjacent tracks to be degraded or lost because of the ATE phenomenon.Further, this first threshold can vary depending upon one or morefactors, e.g., environmental conditions that the device 10 is subjectedto, the composition of the magnetic storage medium 18, the strength ofthe write field, etc.

If the number of times data is written to the first track in the firstregion does not exceed the first predetermined threshold, then, in someembodiments, the number of writes for this track is increased by one inthe lookup table.

If the lookup table is being read from the buffer 62, then the lookuptable stored in the maintenance cylinder can be updated with the lookuptable uploaded to the buffer when the storage device 10 enters an idletime mode or is powered off, for example.

Further, if this first predetermined threshold is not exceeded, then thewrite operation ends at 110.

If, on the other hand, the number of times data is written to the firsttrack in the first region exceeds the first predetermined threshold anddata is rewritten to the second track in the first region of the medium18, then at 112 the number of times this data has been rewritten to thesecond track in the first region is determined. Any suitable techniquesmay be utilized to make this determination. For example, in someembodiments, this determination can be performed by searching a lookuptable where the number of rewrites to an LBA of the second track of thefirst region is recorded when the write command is received.

If the number of times data is rewritten to the second track in thefirst region exceeds a second predetermined threshold (i.e., a secondthreshold amount), then this data is relocated to a second region at116. The second region can be any suitable region of the media 18. Insome embodiments, the second region can be a region that has not beenpreviously allocated for data storage. In other embodiments, the secondregion can be a previously allocated region.

In some embodiments, the second region can be a part of an A-list wheredata from defective sectors of the media 18 are stored. In otherembodiments, the second region can be a part of a temporary list.

In some embodiments, after the data from the second track in the firstregion is relocated to the second region, the LBA of the second track ofthe first region can be rearranged with an LBA of the second region byinterchanging the LBA of the second track in the first region with anLBA of the second region.

The second predetermined threshold for the number of times data isrewritten to the second track in the first region can be any suitablenumber of writes. In some embodiments, this second threshold is at least5 times, at least 10 times, at least 15 times, at least 20 times. Insome embodiments, this threshold is no greater than 1000, 100, etc. Onceagain, this second threshold can, in some embodiments, be determined byestimating the number of times data can be rewritten to the second trackin the first region before the integrity of this data is compromised.Such estimation can be affected by several factors, includingenvironmental conditions that the device 10 is subjected to, thecomposition of the medium 18, and the strength of the magnetic writefield, etc.

In some embodiments, after the data from the second track in the firstregion has been relocated, additional data can be prevented from beingwritten to the second track in the first region. Any suitable techniquecan be utilized to block this region from subsequent write operations.For example, the LBA for the second track in the first region can beremoved from the lookup table.

In some embodiments, if the second region of the media 18 becomes fullyoccupied with data, then the data that was relocated to the secondregion from the second track of the first region can be relocated backto the first region. Any suitable technique can be utilized to relocatethis data. Further, in some embodiments, data from the second region canbe relocated to the second track of the first region when the data fromthe second track in the first region is relocated to the second region.

If the number of times data is rewritten to the second track in thefirst region does not exceed the second predetermined threshold, thenthe writing operation ends at 110. In some embodiments, prior to,during, or after ending the write operation at 110, the number of timesdata has been rewritten to the second track in the first region isincreased by one in the lookup table.

Although the method 100 includes a second track that is adjacent to afirst track or target track, any suitable number of tracks adjacent tothe first track can be rewritten and/or relocated according to thetechniques described herein. For example, in some embodiments, a thirdtrack adjacent to the first track in the first region (i.e., a secondadjacent track) can be positioned such that the first track is betweenthe second track and the third track. Data from this third track can berewritten if the number of times data is written to the first track inthe first region exceeds a third predetermined threshold (i.e., a thirdthreshold amount). The third predetermined threshold can be the same asor different from the first predetermined threshold for rewriting datato the second track in the first region.

Further, the data from the third track can be relocated to any suitableregion of the medium 18 if a number of times data is rewritten to thethird track in the first region exceeds a fourth predetermined threshold(i.e., a fourth threshold amount). This fourth threshold can be the sameas or different from the second predetermined threshold for relocatingdata from the second track in the first region to the second region. Insome embodiments, data from the third track in the first region can berelocated to the second region where data from the second track in thefirst region was relocated. In other embodiments, data from the thirdtrack in the first region can be relocated to a third region that isdifferent from the second region.

The techniques described herein can be utilized with any suitablestorage device or system. For example, in reference to FIG. 1, suchsystem can include a storage medium 18 that includes a first region thathas a first or target track and an adjacent track to the first track(i.e., a second track). The apparatus can also include a controller 50.The controller 50 can be configured to rewrite data from the adjacenttrack if a number of times data is written to the target track exceeds afirst threshold amount (i.e., a first predetermined threshold). Further,in some embodiments, the controller 50 can be configured to relocatedata from the adjacent track in the first region to a second region ofthe storage medium if a number of times data is rewritten to the secondtrack exceeds a second threshold amount (i.e., a second predeterminedthreshold).

In some embodiments, the controller 50 can also be configured toincrease the number of times data is written to the target track in thefirst region by one when the number of times data is written to thetarget track in the first region does not exceed the first thresholdamount. Further, in some embodiments, the controller 50 can also beconfigured to increase the number of times data is rewritten to theadjacent track in the first region by one when the number of times datais rewritten to the adjacent track does not exceed the second thresholdamount.

In some embodiments, the controller 50 can also be configured to rewritedata from a second adjacent track to the first track (i.e., a thirdtrack) in the first region if the number of times data is written to thetarget track exceeds a third threshold amount (i.e., a thirdpredetermined threshold). Further, in some embodiments, the controller50 can be configured to relocate data from the second adjacent track inthe first region to the second region of the storage medium if a numberof times data is rewritten to the second track exceeds a fourththreshold amount (i.e., a fourth predetermined threshold).

In some embodiments, the controller 50 can also be configured to preventadditional data from being written to the adjacent track in the firstregion after data from the adjacent track in the first region isrelocated to the second region of the storage medium. Further, in someembodiments, the controller 50 can also be configured to reassign anaddress of the data that is relocated from the adjacent track in thefirst region to the second region.

Further, in some embodiments, the controller 50 can also be configuredto set the adjacent track in the first region as available memory forstoring other data.

All references and publications cited herein are expressly incorporatedherein by reference in their entirety into this disclosure, except tothe extent they may directly contradict this disclosure. Illustrativeembodiments of this disclosure are discussed and reference has been madeto possible variations within the scope of this disclosure. These andother variations and modifications in the disclosure will be apparent tothose skilled in the art without departing from the scope of thedisclosure, and it should be understood that this disclosure is notlimited to the illustrative embodiments set forth herein. Accordingly,the disclosure is to be limited only by the claims provided below.

In the preceding description, reference is made to the accompanying setof drawings that form a part hereof and in which are shown by way ofillustration several specific embodiments. It is to be understood thatother embodiments are contemplated and may be made without departingfrom the scope or spirit of the present disclosure. The precedingdetailed description, therefore, is not to be taken in a limiting sense.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the properties sought tobe obtained by those skilled in the art utilizing the teachingsdisclosed herein.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, and 5) and any range within that range.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise. As used inthis specification and the appended claims, the term “or” is generallyemployed in its sense including “and/or” unless the content clearlydictates otherwise.

“Include,” “including,” or like terms means encompassing but not limitedto, that is, including and not exclusive. It should be noted that “top”and “bottom” (or other terms like “upper” and “lower”) are utilizedstrictly for relative descriptions and do not imply any overallorientation of the article in which the described element is located.

What is claimed is:
 1. A method comprising: determining a number oftimes data is written to a first track in a first region of a storagemedium; rewriting data from a second track that is adjacent to the firsttrack in the first region if the number of times data is written to thefirst track in the first region exceeds a first predetermined threshold;determining a number of times data is rewritten to the second track inthe first region; and relocating data from the second track in the firstregion to a second region of the storage medium if the number of timesdata is rewritten to the second track in the first region exceeds asecond predetermined threshold.
 2. The method of claim 1, furthercomprising rewriting data from a third track that is adjacent to thefirst track in the first region if the number of times data is writtento the first track in the first region exceeds a third predeterminedthreshold, and the first track is positioned between the second trackand the third track.
 3. The method of claim 2, further comprisingrelocating data from the third track in the first region to the secondregion of the storage medium if a number of times data is rewritten tothe third track in the first region exceeds a fourth predeterminedthreshold.
 4. The method of claim 1, wherein the first predeterminedthreshold is at least 100 times.
 5. The method of claim 1, wherein thesecond predetermined threshold is at least 5 times.
 6. The method ofclaim 1, further comprising preventing additional data from beingwritten to the second track in the first region after relocating datafrom the second track in the first region to the second region of thestorage medium.
 7. The method of claim 1, further comprising reassigningan address of the data that is relocated from the second track in thefirst region to the second region.
 8. The method of claim 1, furthercomprising relocating data that was relocated from the second track inthe first region to the second region back to the first region if thesecond region becomes fully occupied.
 9. A system comprising: a storagemedium comprising a first region with a target track and an adjacenttrack to the target track; and a controller configured to: rewrite datafrom the adjacent track if a number of times data is written to thetarget track exceeds a first threshold amount; and relocate data fromthe adjacent track in the first region to a second region of the storagemedium if a number of times data is rewritten to the second trackexceeds a second threshold amount.
 10. The apparatus of claim 9, whereinthe controller increases the number of times data is written to thetarget track in the first region by one when the number of times data iswritten to the target track in the first region does not exceed thefirst threshold amount.
 11. The apparatus of claim 9, wherein thecontroller increases the number of times data is rewritten to theadjacent track in the first region by one when the number of times datais rewritten to the adjacent track does not exceed the second thresholdamount.
 12. The apparatus of claim 9, wherein the controller is furtherconfigured to rewrite data from a second adjacent track to the targettrack in the first region if the number of times data is written to thetarget track exceeds a third threshold amount.
 13. The apparatus ofclaim 9, wherein the first threshold amount is at least 100 times. 14.The apparatus of claim 9, wherein the second threshold amount is atleast 5 times.
 15. The apparatus of claim 9, wherein the controller isfurther configured to prevent additional data from being written to theadjacent track in the first region after data from the adjacent track inthe first region is relocated to the second region of the storagemedium.
 16. The apparatus of claim 9, wherein the controller is furtherconfigured to reassign an address of the data that is relocated from theadjacent track in the first region to the second region.
 17. Theapparatus of claim 9, wherein the controller is further configured toset the adjacent track in the first region as available memory forstoring other data.
 18. A method comprising: receiving a write command;searching a lookup table where a number of writes to a logical blockaddress (LBA) of a first track in a first region of a storage medium isrecorded when receiving the write command; rewriting data from a secondtrack that is adjacent to the first track in the first region if thenumber of writes of the LBA of the first track of the first regionexceeds a first predetermined threshold of writes; searching a lookuptable where a number of rewrites to an LBA of the second track in thefirst region is recorded when receiving the write command; relocatingdata from the second track in the first region to a second region of thestorage medium if the number of rewrites of the LBA of the second trackin the first region exceeds a second predetermined threshold ofrewrites; and rearranging the LBA of the second track of the firstregion by interchanging the LBA of the second track in the first regionwith an LBA of the second region.
 19. The method of claim 18, whereinthe lookup table is stored in a maintenance cylinder of the magneticstorage medium and uploaded from the maintenance cylinder to a buffer.